The U.S. Government has large stocks of CS1 and CS2, which were formerly employed as lachrymatory agents in burster-type projectiles, but are no longer required and under current plans must be destroyed. CS1 consists of CS, which is essentially o-chlorobenzilidene malononitrile, mixed with approximately 5% by weight of a colloidal silica. The term colloidal silica as used herein refers to extremely finely divided, porous water free silica (Si0.sub.2), having a bulk density ranging about from 2 to 10 lbs./cu. ft. Such colloidal silicas when suspended in a liquid have an ultimate particle size ranging about from 10 to 50 millimicrons. These colloidal silica products are often employed as anticaking agents and as flatting agents for lacquers and are marketed under such trade names as Santocel.RTM. by Monsanto Chemical Co., Cab-o-Sil.RTM. by Godfrey L. Cabot, Inc., and Syloid.RTM. by Davison Chemical Company.
In the manufacture of CS1 and CS2, the CS is micropulverized to particles ranging in size about from 5 to 10 microns and then blended in a tumbler mill or other suitable apparatus with the colloidal silica. In this manner, the colloidal silica is intimately mixed with the CS in such a manner that each particle of CS is coated at least partially with the colloidal silica, which functions as an antiagglomerating and free flow conditioning agent. Because the colloidal silica adheres to the CS particles by physical attraction forces, it is not possible to separate the CS from the colloidal silica by mechanical processes.
The military requires a CS product containing at least 96% o-chlorobenzilidene malononitrile for use in various riot control devices. However, the government supply is insufficient to meet the requirements for CS of such purity in these riot control devices, and the facilities previously employed to manufacture CS used to make CS1 and CS2 have been dismantled. For these reasons, the recovery of CS from CS1 and CS2 is desirable.